A colour digital survey of arcades in Bologna

The purpose is to describe a methodology for the study of the porticos of Bologna with particular reference to the color problem. This study is part of a larger project of research devoted to the study, conservation, enhancement and dissemination of the 'widespread Cultural Heritage' both in territory and in urban areas. Although they constitute a large part of the national heritage and are bearers of great cultural and economic interests, unfortunately they still play a marginal role. The aim of the project is to build a set of methods and an environment based on advanced IC technologies for recording, storage, processing, access and return data for CH in an environment of smart management, reusable data for different purposes by different users (asset management, scientific study, tourism, education, etc..) on preservation technologies (prevention, maintenance and restoration) and sustainable exploitation of cultural heritage. About the 38 kilometers of porticos that contribute to classify the historical center of Bologna as one of the most unique and best preserved in Europe, we have a very fragmentary knowledge. The aim of the study is also to deepen the knowledge of this group of assets through the use of digital technologies survey. The color survey of façades and monumental-historical buildings represents a difficult operation, that becames more sensitive when the goal is to create reality-based 3D digital models. When we need to map 3D models with real-based images the main topic, in the acquisition phase, is to research the relationship between incident light and reflected one, in a specific point above the surface, a problem that, in its general formulation, requires knowledge and control of light sources and the environment influence to the measurements. The use of digital processes for the reproduction of the real color let us to identify color and diffuse reflectance extended to the whole surface artifact, just using few shots and color temperature controlled by software, in order to assure an high accuracy color reproduction of the sample area besides a low cost operation. The methods and survey instruments used are different, in particular, we refer to: photo modeling, survey through instrumental laser scanner and total station. We propose a comparison between the various methods and results (3D models, orthophoto, etc.) in order to optimize these results for two user profiles: the technical and the management of touris